An Intricate Mechanism of Action of Avonex in Relapsing Remitting Multiple Sclerosis Patients: Variation of Serum Titre of Interleukin-17A, Interleukin-10 and Transforming Growth Factor-β

Introduction: The immunopathogenesis of multiple sclerosis (MS) is a main field of research, together with the mechanism of action of most immune therapies in this disease, such as interferon beta. Interleukin (IL)-17 is considered to play a central part in the initial immune cascade in MS, though there are numerous interactions between other cytokines that might explain the heterogeneity of disease evolution and treatment response. Material and Methods: We tested the serum levels of IL-17A, IL-10 and transforming growth factor (TGF-β) using the enzyme-linked immunosorbent assay method in three small groups of relapsing-remitting MS patients: 10 being naïve without treatment, 10 patients receiving Avonex treatment early in the MS evolution (≤ one year from the MS onset) and 12 MS patients who received Avonex later in the disease evolution. The values were compared with those obtained from 32 healthy subjects using statistical analysis. Results: In the naive multiple sclerosis group: IL-17A values were statistically higher than among healthy subjects; IL- 17A inversely correlated with MS duration; serum IL-17A negatively correlated with TGF-β. A direct correlation was found between the serum titre of IL-17A and IL-10 in the early treated multiple sclerosis group; the titre of IL-17A was significantly reduced compared with that from the late treated multiple sclerosis group. Conclusion: The role in MS pathology of IL-17A, IL-10 and TGF-β is only partially elucidated. IL-17 plays an important role in the inflammatory phase of relapsing-remitting MS and is diminished by Avonex mainly if this disease modifying treatment is administered early in the evolution of MS.